Divergent Synthesis of Graft and Branched Copolymers through Spatially Controlled Photopolymerization in Flow Reactors

Abstract

In this work, we demonstrate the controlled synthesis of graft and branched copolymers using one-pot (batch) or one-pass (flow) processes without intermediate purification. The formation of poly­(methacrylate) copolymers with pendent reversible addition–fragmentation chain transfer (RAFT) agent functionalities was performed using a selective photoactivation approach in the first step, specifically via green light-mediated direct photoRAFT polymerization. A nonselective photoinduced chain extension using red light-triggered photoinduced energy/electron transfer (PET)-RAFT polymerization was then performed to provide tailored graft copolymers. Notably, the application of this protocol to a flow process with two spatially segregated unit operations provides a route to independent control of the backbone-forming step (unit operation one) and the subsequent chain extensions (unit operation two). By alternating the light sources in both unit operations between the On and Off states, a range of macromolecular architectures could be prepared from the same starting materials. To demonstrate the power of this divergent approach, a series of graft copolymers with tailored backbone lengths and number and molecular weight characteristics of side chains were synthesized using the same starting materials by a single pass process. Additionally, the polymer architecture was switched between graft and hyperbranched architectures via external manipulation of light sources.

Double thermoresponsive graft copolymers with different chain ends: feasible precursors for covalently crosslinked hydrogels

“…Recently, photoiniferter polymerization was found to be a more efficient route for the preparation of polymers with graft or brush structures. [21][22][23][24] In 2018, a catalyst-free photoiniferter RAFT polymerization that was selectively initiated by two kinds of visible light irradiation was introduced for the preparation of graft copolymers. 22 In that study, methyl methacrylate (backbone) was polymerized via photoiniferter RAFT under green light irradiation, while N,N-dimethylacrylamide (side chains) was polymerized under blue light irradiation.…”

Computer‐Aided Living Polymerization Conducted under Continuous‐Flow Conditions†

“…MWD profile, polymer sequence and topology are important factors to determine polymer properties ( e.g ., mechanical performance, self‐assembly behavior, thermal properties). [ 69‐74 ] However, the on‐demand regulation of such factors is quite challenging, and was manually probed via batch‐to‐batch operations in past many years. [ 75‐76 ]…”

Playing construction with the monomer toy box for the synthesis of multi‐stimuli responsive copolymers by reversible deactivation radical polymerization protocols

“…PISA achieves solvent‐economy by definition, RDRPs can be carried out in alcoholic and aqueous solvents, and photopolymerization 243 allows lower reaction temperatures. In this context, photoinitiation and photomodulation of RAFT is extensively researched 158,159,244–248 . Another issue to be addressed is deoxygenation of the reaction mixture, which is normally achieved through inert atmosphere or freeze‐pump‐thaw cycles.…”